Tin oxide overcoat indium tin oxide coatings, coated glazings, and production methods

ABSTRACT

The invention provides transparent conductive coatings based on indium tin oxide. The coating has a tin oxide overcoat. In some embodiments, the coating further includes one or more overcoat films comprising silicon nitride, silicon oxynitride, or silica. The coating and its films have compositions, thicknesses, and properties that simultaneously produce low sheet resistance and high visible transmission, preferably together with neutral color properties and good durability.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Utility application Ser.No. 14/807,624, filed on Jul. 23, 2015; U.S. Utility application Ser.No. 14/185,287, filed on Feb. 20, 2014 and now issued as U.S. Pat. No.9,453,365; U.S. Utility application Ser. No. 13/006,992, filed on Jan.14, 2011 and now issued as U.S. Pat. No. 8,658,262; and U.S. ProvisionalApplication No. 61/295,694, filed on Jan. 16, 2010, each of which ishereby incorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to thin film coatings for glass and othersubstrates. In particular, this invention relates to transparentelectrically conductive coatings based on indium tin oxide. Alsoprovided are methods and equipment for producing such coatings andglazing assemblies.

BACKGROUND OF THE INVENTION

A variety of transparent electrically conductive oxide (TCO) coatingsare known in the art. Commonly, these coatings include an indium tinoxide film. In some cases, the indium tin oxide film is located beneathone or more overcoat films of silicon nitride, silicon oxynitride, orsilicon dioxide. It would be desirable to provide an overcoat film that:(i) has a composition different from that of the TCO film, and yet (ii)contains a metal also found in the TCO film. It would be particularlydesirable to provide an overcoat film of this nature that provides thecoating with exceptional durability and adheres particularly well toindium tin oxide film and any overcoat films of silicon nitride, siliconoxynitride, or silicon dioxide. In such cases, it would be desirable forthe coating and its films to have compositions and thicknesses thatsimultaneously achieve low sheet resistance and high visibletransmission, preferably together with neutral color properties.

BRIEF SUMMARY OF THE INVENTION

Certain embodiments of the invention provide a multiple-pane insulatingglazing unit having a between-pane space and two opposed external panesurfaces. A desired one of the two external pane surfaces bears acoating comprising both an indium tin oxide film and a tin oxide film.The tin oxide film is located over the indium tin oxide film.

In some embodiments, the invention provides a coated pane comprising aglass substrate and a coating on the glass substrate. The coatingcomprises both an indium tin oxide film and a tin oxide film. The tinoxide film is located further from the glass pane than is the indium tinoxide film. In the present embodiments, the indium tin oxide film has athickness of between 100 Å and 2,000 Å, while the tin oxide film has athickness of between 90 Å and 1,200 Å. Preferably, the indium tin oxidefilm has a sheet resistance of less than 20 ohms/square, while thecoated pane has a visible transmission of greater than 75%.

Some embodiments provide a multiple-pane insulating glazing unit havinga between-pane space and two opposed external pane surfaces. A desiredone of the two external pane surfaces bears a coating comprising both anindium tin oxide film and a tin oxide film. The tin oxide film islocated over the indium tin oxide film. In the present embodiments, theindium tin oxide film has a sheet resistance of less than 20 ohms/squareand a thickness of between 1,000 Å and 1,600 Å. Preferably, the tinoxide film has a thickness of between 90 Å and 1,200 Å, and is devoid ofindium oxide. In the present embodiments, the multiple-pane insulatingglazing unit includes an internal pane surface bearing a low-emissivitycoating that has only one film comprising silver. The film comprisingsilver contains at least 50% silver by weight. The low-emissivitycoating is exposed to the between-pane space. The multiple-paneinsulating glazing unit has a U value of less than 0.25 together with avisible transmission of greater than 75%, and the multiple-paneinsulating glazing unit exhibits an exterior reflected colorcharacterized by an “an” color coordinate of between −6 and 0 and a“b_(h)” color coordinate of between −8 and −1.

Certain embodiments provide a multiple-pane insulating glazing unithaving a between-pane space and two opposed external pane surfaces. Adesired one of the two external pane surfaces bears a coating comprisingboth an indium tin oxide film and a tin oxide film. The tin oxide filmis located over the indium tin oxide film. In the present embodiments,the indium tin oxide film has a sheet resistance of less than 20ohms/square, and a thickness of between 1,000 Å and 1,600 Å. Preferably,the tin oxide film has a thickness of between 90 Å and 1,200 Å, and isdevoid of indium oxide. In the present embodiments, the multiple-paneinsulating glazing unit includes an internal pane surface bearing alow-emissivity coating that has only two films comprising silver. Eachof the two films comprising silver contains at least 50% silver byweight. The low-emissivity coating is exposed to the between-pane space.The multiple-pane insulating glazing unit has a U value of less than0.25 together with a visible transmission of greater than 65%, and themultiple-pane insulating glazing unit exhibits an exterior reflectedcolor characterized by an “a_(h)” color coordinate of between −6 and 0and a “b_(h)” color coordinate of between −8 and −1.

Further, some embodiments provide a multiple-pane insulating glazingunit having a between-pane space and two opposed external pane surfaces.A desired one of the two external pane surfaces bears a coatingcomprising both an indium tin oxide film and a tin oxide film. The tinoxide film is located over the indium tin oxide film. In the presentembodiments, the indium tin oxide film has a sheet resistance of lessthan 20 ohms/square, and a thickness of between 1,000 Å and 1,600 Å.Preferably, the tin oxide film has a thickness of between 90 Å and 1,200Å, and is devoid of indium oxide. In the present embodiments, themultiple-pane insulating glazing unit includes an internal pane surfacebearing a low-emissivity coating that includes three films comprisingsilver. Each of the films comprising silver contains at least 50% silverby weight. The low-emissivity coating is exposed to the between-panespace. The multiple-pane insulating glazing unit has a U value of lessthan 0.25 together with a visible transmission of greater than 60%, andthe multiple-pane insulating glazing unit exhibits an exterior reflectedcolor characterized by an “an” color coordinate of between −6 and 1 anda “b_(h)” color coordinate of between −7 and −1.

Still further, certain embodiments of the invention provide a coatedpane comprising a glass substrate and a coating on the glass substrate.The coating includes both an indium tin oxide film and a tin oxide film.The tin oxide film is located further from the glass pane than is theindium tin oxide film. In the present embodiments, the coating has anemissivity in the range of from 0.25 to 0.55, and the coated pane has avisible transmission of greater than 75%. Preferably, the indium tinoxide film has a thickness of greater than 100 Å but less than 1,100 Å,and the tin oxide film has a thickness of between 90 Å and 1,200 Å.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a broken-away schematic cross-sectional view of a substratehaving a major surface bearing a transparent electrically conductivecoating in accordance with certain embodiments of the present invention;

FIG. 2 is a broken-away schematic cross-sectional view of a substratehaving a major surface bearing a transparent electrically conductivecoating in accordance with other embodiments of the invention;

FIG. 3 is a broken-away schematic cross-sectional view of a substratehaving a major surface bearing a transparent electrically conductivecoating in accordance with still other embodiments of the invention;

FIG. 4 is a broken-away schematic cross-sectional view of a substratehaving a major surface bearing a transparent electrically conductivecoating in accordance with yet other embodiments of the invention;

FIG. 5 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the interior pane having a fourth surface carryinga transparent electrically conductive coating in accordance with certainembodiments of the invention;

FIG. 6 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the exterior pane having a first surface carryinga transparent electrically conductive coating, and the interior panehaving a fourth surface carrying another transparent electricallyconductive coating, in accordance with certain embodiments of theinvention;

FIG. 7 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the exterior pane having a first surface carryinga hydrophilic and/or photocatalytic film, and the interior pane having afourth surface carrying a transparent electrically conductive coating,in accordance with certain embodiments of the invention; and

FIG. 8 is a partially broken-away schematic cross-sectional side view ofa multiple-pane insulating glazing unit that includes an exterior paneand an interior pane, the exterior pane having a second surface carryinga low-emissivity coating, and the interior pane having a fourth surfacecarrying a transparent electrically conductive coating, in accordancewith certain embodiments of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description is to be read with reference to thedrawings, in which like elements in different drawings have likereference numerals. The drawings, which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention. Skilled artisans will recognize that the examplesprovided herein have many useful alternatives that fall within the scopeof the invention.

Many embodiments of the invention involve a coated substrate. A widevariety of substrate types are suitable for use in the invention. Insome embodiments, the substrate is a sheet-like substrate havinggenerally opposed first and second major surfaces. For example, thesubstrate can be a sheet of transparent material (i.e., a transparentsheet). The substrate, however, is not required to be a sheet, nor is itrequired to be transparent.

For many applications, the substrate will comprise a transparent (or atleast translucent) material, such as glass or clear plastic. Forexample, the substrate is a glass sheet (e.g., a window pane) in certainembodiments. A variety of known glass types can be used, such assoda-lime glass. In some cases, it may be desirable to use “whiteglass,” a low iron glass, etc. In certain embodiments, the substrate ispart of a window, door, skylight, or other glazing. Depending on thelevel of solar control desired, the present coating may be applied totinted glass. Thus, the coating of any embodiment disclosed herein canoptionally be provided on a sheet of tinted glass. This may provideparticularly good selectivity.

Substrates of various sizes can be used in the present invention.Commonly, large-area substrates are used. Certain embodiments involve asubstrate having a major dimension (e.g., a length or width) of at leastabout 0.5 meter, preferably at least about 1 meter, perhaps morepreferably at least about 1.5 meters (e.g., between about 2 meters andabout 4 meters), and in some cases at least about 3 meters. In someembodiments, the substrate is a jumbo glass sheet having a length and/orwidth that is between about 3 meters and about 10 meters, e.g., a glasssheet having a width of about 3.5 meters and a length of about 6.5meters. Substrates having a length and/or width of greater than about 10meters are also anticipated.

Substrates of various thicknesses can be used in the present invention.In some embodiments, the substrate (which can optionally be a glasssheet) has a thickness of about 1-8 mm. Certain embodiments involve asubstrate with a thickness of between about 2.3 mm and about 4.8 mm, andperhaps more preferably between about 2.5 mm and about 4.8 mm. In oneparticular embodiment, a sheet of glass (e.g., soda-lime glass) with athickness of about 3 mm is used.

The substrate 10′ has opposed surfaces 16 and 18, which preferably areopposed major surfaces. In some cases, surface 16 is destined to be aninternal surface exposed to a between-pane space of an insulatingglazing unit, while surface 18 is destined to be an external surfaceexposed to an interior of a building. This, however, will not be thecase in all embodiments.

As shown in FIGS. 1 and 2, the substrate 10′ bears a transparentelectrically conductive coating 7. In FIG. 1, the coating 7 includes, insequence from surface 18 outwardly, an indium tin oxide film 20 and atin oxide film 100. In FIG. 2, the coating 7 includes, from surface 18outwardly, an optional base film 15, the indium tin oxide film 20, andthe tin oxide film 100. The films 15, 20, and 100 can be provided in theform of discrete layers, thicknesses of graded film, or a combination ofboth including at least one discrete layer and at least one thickness ofgraded film. While the base film 15 is shown as a single layer, it canalternatively be a plurality of layers. Preferably, all the films in thecoating 7 are oxide, nitride, or oxynitride films. In some cases, allthe films in the coating 7 are sputtered films.

The coating 7 preferably is formed of materials, and made by a process(as detailed herein), that allows the coated substrate to have a hazelevel of less than 0.5 or less than 0.3 (e.g., less than 0.2, less than0.1, or even less than 0.09), a roughness R_(a) of less than about 10nm, less than about 5 nm, or less than about 3 nm (e.g., less than about2 nm), and a monolithic visible transmission of greater than 75%(preferably greater than 80%).

Haze can be measured in well-known fashion, e.g., using a BYK Haze-Gardplus instrument. Reference is made to ASTM D 1003-00: Standard Testmethod for Haze and Luminous Transmittance of Transparent Plastics, thecontents of which are incorporated herein by reference.

In certain embodiments, the coated substrate has a haze of less than 0.3and a surface roughness of about less than 3 nm, together with amonolithic visible transmission of greater than 70% (e.g., before andafter heat treatment), greater than 73% (e.g., before and after heattreatment), greater than 81% (e.g., after heat treatment), greater than82% (e.g., after heat treatment), or even greater than 85% in some cases(e.g., after heat treatment), in combination with a post-heat R_(sheet)of less than 75 ohms/square, less than 55 ohms/square, less than 30ohms/square, less than 15 ohms/square, or in some cases even less than13 ohms/square, such as about 11.5 to 12.5 ohms/square.

The coating 7 also has a low surface roughness. Preferably, the coating7 has a surface roughness R_(a) of less than 10 nm, less than 5 nm, lessthan 3 nm, less than 2.5 nm, less than 2.2 nm, or even less than 2.0 nm,such as about 1.9 nm. The deposition method and conditions preferablyare chosen so as to provide the coating with such a roughness.Alternatively, the coating could be polished after deposition to reduceits surface roughness. Preferably, though, the coating exhibits thepreferred surface roughness without requiring any polishing or the like(e.g., as-deposited).

Surface roughness is defined in terms deviations from the mean surfacelevel. The surface roughness R_(a) is the arithmetical mean surfaceroughness. This is the arithmetic average of the absolute deviationsfrom the mean surface level. The arithmetical mean surface roughness ofa coating is commonly represented by the equation: R_(a)=1/L ∫₀^(L)|f(x)|dx.” The surface roughness R_(a) can be measured inconventional fashion, e.g., using an Atomic Force Microscope (AFM)equipped with conventional software that gives R_(a).

When provided, the optional base film 15 can comprise, consistessentially of, or consist of silica, alumina, or a mixture of both. Inother embodiments, the base film 15 comprises titanium dioxide. In stillother embodiments, the base film 15 comprises tin oxide (e.g., SnO₂). Insuch embodiments, the base film 15 may be devoid of indium. For example,a base film 15 consisting of (or at least consisting essentially of) tinoxide is provided in some cases. Combinations of two or more of silica,alumina, titanium dioxide, and tin oxide may be used as well.Alternatively, other dielectric films may be used.

Thus, in certain embodiments, in addition to the indium tin oxide film20, the coating 7 includes a film 15 comprising tin oxide located underthe indium tin oxide film 20 in combination with a tin oxide film 100located over the indium tin oxide film 20.

The indium tin oxide film 20 comprises indium tin oxide optionallytogether with one or more other materials. If desired, zinc, aluminum,antimony, fluorine, carbon nanotubes, or other additives can be includedin the film. Preferably, the indium tin oxide film 20 consistsessentially of, or consists of, indium tin oxide. The indium tin oxidefilm 20 can contain various relative percentages of indium oxide and tinoxide. Indium oxide is the major constituent. That is, it accounts formore than 50% of the film's total weight. Preferably, the composition ofthe film ranges from about 75% indium oxide/25% tin oxide to about 95%indium oxide/5% tin oxide, such as about 90% indium oxide/10% tin oxide.

The tin oxide film 100 is located over the indium tin oxide film 20. Insome cases, the tin oxide film 100 comprises fluorine. Preferably, thetin oxide film 100 is devoid of indium oxide. For example, the tin oxidefilm 100 may consist of (or at least consist essentially of) tin oxide(e.g., SnO₂). In certain embodiments, film 100 contains at least 75% tinoxide, at least 85% tin oxide, or at least 95% tin oxide (based on thetotal weight of the film), while also being devoid of indium oxide.

The coating 7 can optionally include a nitride film between the indiumtin oxide film and the tin oxide film. The nitride film may comprise oneor more of silicon nitride, aluminum nitride, and titanium nitride. Forexample, a thin film of silicon nitride can optionally be positioneddirectly between (i.e., so as to contact both) the indium tin oxide filmand the tin oxide film. When provided, this silicon nitride film (whichcan optionally include a small amount of aluminum) may have a thicknessof less than 250 Å, or even less than 200 Å, e.g., about 150 Å.

In other embodiments, the tin oxide film 100 is in contact with theindium tin oxide film 20. Providing the tin oxide film 100 directly over(i.e., so as to be in contact with) the underlying indium tin oxide film20 can be advantageous in that, while these two films have differentcompositions, both contain tin oxide and may provide exceptionaladhesion to each other. This film combination may also make the coatingparticularly smooth, thus creating a coated surface that is easier toclean, remove label residue, etc.

When provided, the optional base film 15 has a thickness of 50 Å ormore, such as about 70-300 Å. In certain embodiments, the coatingincludes a base film of silica (optionally including some aluminum),alumina, titanium dioxide, or tin oxide at a thickness of 75-150 Å.

In other embodiments, the indium tin oxide film 20 is directly on (i.e.,in contact with) the substrate surface 18. In these embodiments, thereis of course no base film 15. Applicant has found that good results canbe achieved in cases where indium tin oxide film is directly onsoda-lime float glass.

Preferably, the indium tin oxide film 20 has a thickness of between 100Å and 2,000 Å. In certain embodiments, the indium tin oxide film 20 hasa thickness of less than 1,750 Å, such as between 1,000 Å and 1,600 Å,or even less than 1,500 Å, such as about 1,200-1,400 Å. The thicknessesrecited herein are physical thicknesses unless otherwise specified to beoptical thicknesses.

The indium tin oxide film 20 preferably has a sheet resistance of lessthan 55 ohms/square. In certain embodiments, the sheet resistance isless than 20 ohms/square, or even less than 15 ohms/square, such asabout 11.5-12.5 ohms/square.

The tin oxide film 100 can have a thickness of between 90 Å and 1,200 Å.In certain embodiments, the film 100 has a thickness of between 100 Åand 600 Å, such as between 200 Å and 400 Å, e.g., about 350 Å.

Some embodiments provide the thickness of the indium tin oxide film 20in the range of about 1,100-1,500 Å in combination with the thickness ofthe tin oxide film 100 being about 100-700 Å. This combination ofthicknesses, however, is not required for all embodiments. Rather, thiscombination of thicknesses is merely used in one group of embodiments.This combination of thicknesses, however, can optionally be provided inany embodiment hereof (i.e., in any embodiment having any of the notedcombinations of other features and properties described herein).

Table 1 below shows four exemplary film stacks that can be used ascoating 7 (here, it will be appreciated that the tin oxide film is theoutermost film of the coating):

TABLE 1 FILM SAMPLE A SAMPLE B SAMPLE C SAMPLE D ITO 1,325 Å 1,250 Å1,240 Å 1,350 Å SnO₂   440 Å   560 Å   600 Å   460 Å

These film stacks represent a broader group of embodiments wherein thecoating 7 has a total thickness of less than 2,400 Å. A base film (e.g.,silica at about 100 Å) can optionally be added. Additionally oralternatively, a nitride film (e.g., silicon nitride at about 150 Å) maybe added between the ITO and SnO₂ films.

The coating 7 can optionally further include an oxynitride film 90located over the tin oxide film 100. Reference is made to FIG. 3. Whenprovided, the oxynitride film 90 can have a thickness of between 100 Åand 1,300 Å, such as between 400 angstroms and 900 angstroms. Theoxynitride film 90 can optionally be directly over (i.e., so as tocontact) the tin oxide film 100. The oxynitride film 90 may comprisealuminum, oxygen, and nitrogen. In certain embodiments, the oxynitridefilm 90 is an exposed outermost film of the coating 7.

In some cases, the oxynitride film 90 comprises silicon oxynitride at athickness of between 400 Å and 900 Å. The silicon oxynitride may, forexample, be sputter deposited from one or more silicon-aluminum targets,such as elemental targets comprising a sputterable material consistingof about 83% silicon and 17% aluminum.

In certain embodiments, the coating 7 includes a film comprisingtitanium oxide 70. When provided, the film comprising titanium oxide 70can be located over the tin oxide film 100. Furthermore, when both theoptional oxynitride film 90 and the optional film comprising titaniumoxide 70 are provided, the film comprising titanium oxide is locatedover the oxynitride film. In preferred embodiments, the film comprisingtitanium oxide 70 has a thickness of less than 200 Å, such as from 10-75Å, e.g., about 50 Å.

Preferably, the film comprising titanium oxide 70 is photocatalytic,hydrophilic, or both. Suitable films are described in U.S. Patent andApplication Nos. 7,294,404 and 11/129,820 and 7,713,632 and 7,604,865and 11/293,032 and 7,862,910 and 7,820,309 and 7,820,296, the salientteachings of each of which are incorporated herein by reference.

In some embodiments, the coated substrate 10′ is part of a monolithicglazing. In other embodiments, the coated substrate 10′ is part of amulti-pane insulating glazing unit (“IG unit”) 110.

In one group of embodiments, the coating 7 is on a #4 surface, a #6surface, or another external surface of the inboard pane of an IG unit100. By providing the transparent electrically conductive coating 7 onthis surface, the temperature of this indoor pane under certainconditions can be decreased. In such cases, by providing aphotocatalytic and/or hydrophilic film comprising titanium oxide 70 overthe rest of the coating 7, any condensation that may occur on theroom-side surface may be more readily formed into a sheet andevaporated.

Thus, certain embodiments provide a coated substrate (e.g., a glasspane) having the following films in sequence moving outwardly from thesubstrate (though, not necessarily in contiguous sequence): indium tinoxide film/tin oxide film/film comprising titanium oxide, or: indium tinoxide film/tin oxide film/oxynitride film/film comprising titaniumoxide. The film comprising titanium oxide can be, for example, a TiO₂film or a film comprising both titanium oxide and tungsten oxide (e.g.,about 2.5% W). The film comprising titanium oxide can have a physicalthickness of less than 200 Å, or even less than 75 Å, such as about 50Å. In the present embodiments, the film comprising titanium oxide 70 canbe the outermost (i.e., exposed) film of the coating 7.

Referring to the embodiments of FIGS. 5-8, the “first” (or “#1”) surfaceis exposed to an outdoor environment. Accordingly, it is the #1 surfacethat radiation from the sun first strikes. The external surface of theoutboard pane is the so-called first surface. Moving from the #1 surfacetoward the interior of the building, the next surface is the “second”(or “#2”) surface. Thus, the internal surface of the outboard pane isthe so-called second surface. Moving further toward the interior of thebuilding, the next surface is the “third” (or “#3”) surface, followed bythe “fourth” (or “#4”) surface. This convention is carried forward forIG units having more than four major pane surfaces. Thus, for atriple-pane IG unit, the #6 surface would be the external surface of theinboard pane.

One group of embodiments provides a triple glazing (e.g., an IG unithaving three panes), and coating 7 is provided on the #6 surface of theglazing. In embodiments of this nature, the #1 and/or #2 surfaces mayhave other functional coatings. The #1 surface, for example, may alsohave a transparent electrically conductive coating 7′, and/or the #2surface may have a silver-based low-emissivity coating.

In some cases, the substrate 10′ is heated prior to film deposition,during deposition, or both. Additionally or alternatively, the coatedsubstrate 10′ can be heat treated after being coated. If desired, thepost-deposition heat treatment (such as glass tempering) can beperformed in air. When the coated substrate 10′ is heat treated, defectsin the film can be healed and improvement of crystalline structure canoccur in the indium tin oxide film 20 without an uncontrollable changein the chemistry of the transparent conductive film 20. The tin oxidefilm 100, optionally together with one or more overlying films of thenature described above, may provide resistance to oxygen reaching andreacting with the indium tin oxide film 20 so as to cause uncontrollablechange in its chemistry during heat treatment. The film materials andthicknesses described herein are believed to be suitable foraccomplishing this object.

In certain embodiments, the coating 7 is on a glass pane, and thiscoated glass pane is heat treated through a process that leaves thecoated glass cut-able by conventional glass cutting techniques. The heattreatment, for example, can involve using lower temperature forconversion so as to maintain the stress in the glass such that thecoated glass remains cut-able even after the heat treatment.

In FIGS. 5-8, the substrate 10′ is a transparent pane that is part of anIG unit 110. Commonly, the IG unit 110 has an exterior pane 10 and aninterior pane 10′ separated by at least one between-pane space 800. Aspacer 900 (which can optionally be part of a sash) is provided toseparate the panes 10 and 10′. The spacer 900 can be secured to theinternal surfaces of each pane using an adhesive or seal 700. In somecases, an end sealant 600 is also provided. In the illustratedembodiments, the exterior pane 10 has an external surface 12 (the #1surface) and an internal surface 14 (the #2 surface). The interior pane10′ has an internal surface 16 (the #3 surface) and, in some cases(i.e., when the IG unit is a double-pane unit), an external surface 18(the #4 surface). In other embodiments, the IG unit 110 has three panes,such that the external surface 18 of the interior pane 10′ is the #6surface.

The IG unit can optionally be mounted in a frame (e.g., a window sash orframe) such that the external surface 12 of the exterior pane 10 isexposed to an outdoor environment 77 while the external surface 18 ofthe interior pane 10′ is exposed to a room-side interior environment.Each internal surface of the unit is exposed to a between-pane space 800of the IG unit. In some embodiments, the IG unit 100 is a vacuum IGunit.

The IG unit 110 includes a transparent electrically conductive coating 7in accordance with any embodiment described herein. In the embodiment ofFIG. 5, the external surface 18 of pane 10′ bears a transparentelectrically conductive coating 7. Here, the illustrated coating 7 isexposed to an environment (in some cases, a temperature-controlledliving space) inside a home or another building.

The IG unit 110 can further include one or more films comprisingtitanium oxide 70, such as a hydrophilic and/or photocatalytic film. Inthe embodiment of FIG. 7, for example, a film comprising titanium oxide70 is provided on the external surface 12 of pane 10, so as to beexposed to an outdoor environment 77 (and thus in periodic contact withrain). The film comprising titanium oxide 70 can be part of aphotocatalytic and/or hydrophilic coating. If desired, the IG unit 110can bear two films comprising titanium oxide, e.g., one such film 70 onthe external surface 12 of pane 10 and another such film 70 over therest of the coating 7 on the external surface 18 of pane 10′.

Thus, in some cases, there are two films comprising titanium oxide 70 onthe IG unit. When provided, these two coatings may be different. Forexample, the external surface of the outboard pane and the externalsurface of the inboard pane can both have photocatalytic films, but theycan be different (e.g., in terms of thickness or composition). Forexample, a photocatalytic film on the external surface of the inboardpane can be adapted for activation by indoor light, while aphotocatalytic film on the external surface of the outboard pane mayrequire direct sunlight for activation. More generally, the indoorphotocatalytic film may have a higher level of photoactivity (e.g., itmay be thicker or have a more highly photoactive composition) than theoutside photocatalytic film. When provided, the films comprisingtitanium may, of course, be applied over one or more other films.

The IG unit 110 may also include one or more low-emissivity coatings 80.In the embodiment of FIG. 8, the IG unit includes a low-emissivitycoating 80 on the internal surface 14 of pane 10. When provided, thelow-emissivity coating 80 preferably includes at least onesilver-inclusive film, which preferably contains more than 50% silver byweight (e.g., a metallic silver film). If desired, a low-emissivitycoating 80 can alternatively be on the internal surface 16 of pane 10′.In some embodiments, the coating 80 includes three or moreinfrared-reflective films (e.g., silver-containing films).Low-emissivity coatings with three or more infrared-reflective films aredescribed in U.S. Patent and Application Nos. 11/546,152 and 7,572,511and 7,572,510 and 7,572,509 and 11/545,211 and 7,342,716 and 7,339,728,the salient teachings of each of which are incorporated herein byreference. In other cases, the low-emissivity coating can be a “singlesilver” or “double silver” low-emissivity coating, which are well-knownto skilled artisans.

If desired, the embodiment of FIG. 6 can have a low-emissivity coatingon surface 14 or on surface 16. Similarly, the embodiment of FIG. 7 canoptionally have a low-emissivity coating on surface 14 or on surface 16.

While the embodiment of FIG. 5 shows the transparent electricallyconductive coating 7 being on the #4 surface of an IG unit 110, the #1surface of the IG unit can alternatively be provided with a transparentelectrically conductive coating. In such cases, there can optionally bea low-emissivity coating on surface 14 or on surface 16.

FIG. 6 shows an IG unit 110 having a first transparent electricallyconductive coating 7 on the #4 surface of the IG unit, while a secondtransparent electrically conductive coating 7′ is on the #1 surface ofthe IG unit. For triple glazed IG units, a first transparentelectrically conductive coating can be provided on the #6 surface of theIG unit, while a second transparent electrically conductive coating isprovided on the #1 surface of the IG unit. Or, there can simply be asingle transparent electrically conductive coating on the #1 surface.

Thus, it can be appreciated that the transparent electrically conductivecoating 7 may be provided on one or more of the following IG unitsurfaces: the #1 surface, the #4 surface (for a double glazing), and the#6 surface (for a triple glazing). When applied on the #1 surface, thepane will stay warmer and have less condensation. When applied on a #4or #6 surface, the inboard pane will stay cooler and save energy, but itmay catch condensation. In such cases, a hydrophilic and/orphotocatalytic coating may be provided over coating 7 so as to encouragerapid evaporation of any condensation that may occur. The transparentelectrically conductive coating 7 can also be beneficial for amonolithic glazing, a laminated glass glazing, etc.

The present coating 7 has a number of beneficial properties. The ensuingdiscussion reports several of these properties. In some cases,properties are reported herein for a single (i.e., monolithic) pane 10′bearing the present coating 7 on one surface 18 (“the present pane”). Inother cases, these properties are reported for a double-pane IG unit 110having the transparent electrically conductive coating 7 on the #4surface 18 and a triple silver low-emissivity coating on the #2 surface.The triple silver low-emissivity coating is known commercially as theLoE³- 366™ product from Cardinal CG Company. In such cases, the reportedproperties are for an IG unit wherein both panes are clear 2.2 mm sodalime float glass with a ½ inch between-pane space filled with aninsulative gas mix of 90% argon and 10% air (“the present IG unit”). Ofcourse, these specifics are by no means limiting to the invention. Forexample, the transparent electrically conductive coating canalternatively be provided on the #1 surface of the IG unit, thelow-emissivity coating can alternatively be on the #3 surface, thelow-emissivity coating can alternatively be a single or double silverlow-emissivity coating, etc. Absent an express statement to thecontrary, the present discussion reports determinations made using thewell-known WINDOW 7.1 computer program (e.g., calculating center ofglass data) under NFRC100-2010 conditions.

As already explained, the indium tin oxide 20 is electrically conductiveand imparts low sheet resistance in the coating 7. The sheet resistanceof the present coating 7 is less than 75Ω/square. Preferably, the sheetresistance of this coating 7 is 55Ω/square or less, such as less than20Ω/square (e.g., less than 15Ω/square, less than 14Ω/square, or evenless than 13Ω/square). The sheet resistance of the coating can bemeasured in standard fashion using a non-contact sheet resistance meter.

The coating 7 also has low emissivity. The emissivity of the coating 7is less than 0.75. Preferably, the emissivity is 0.55 or less, such asless than 0.25, less than 0.22, less than 0.2, or even less than 0.18,such as about 0.15. In contrast, an uncoated pane of clear glass wouldtypically have an emissivity of about 0.84.

The term “emissivity” is well known in the present art. This term isused herein in accordance with its well-known meaning to refer to theratio of radiation emitted by a surface to the radiation emitted by ablackbody at the same temperature. Emissivity is a characteristic ofboth absorption and reflectance. It is usually represented by theformula: E=1−Reflectance. The present emissivity values can bedetermined as specified in “Standard Test Method for Emittance ofSpecular Surfaces Using Spectrometric Measurements,” NFRC 301-2010, theentire teachings of which are incorporated herein by reference.

In addition to low sheet resistance and low emissivity, the U Value ofthe present IG unit 110 is very low. As is well known, the U Value of anIG unit is a measure of the thermal insulating property of the unit. Thesmaller the U value, the better the insulating property of the unit. TheU Value of the present IG unit is less than 0.35 (i.e., center of glassU value), preferably less than 0.3, more preferably less than 0.25, andperhaps optimally less than 0.24, such as from 0.20-0.23.

The term U Value is well known in the present art. It is used herein inaccordance with its well-known meaning to express the amount of heatthat passes through one unit of area in one unit of time for each unitof temperature difference between a hot side of the IG unit and a coldside of the IG unit. The U Value can be determined in accordance withthe standard specified for U_(winter) in NFRC 100-2014, the teachings ofwhich are incorporated herein by reference.

A tradeoff is sometimes made in low U value coatings whereby the film(s)selected to achieve a low U value have the effect of decreasing thevisible transmittance to a lower level than is desired and/or increasingthe visible reflectance to a higher level than is ideal. As aconsequence, windows bearing these coatings may have unacceptably lowvisible transmission, a somewhat mirror-like appearance, or suboptimalcolor properties.

In combination with the beneficial properties discussed above, thepresent coating 7 has good optical properties. As noted above, atradeoff is sometimes made in low U value coatings whereby the filmsselected to achieve a low U value have the effect of restricting thevisible transmission to a level that is lower than ideal.

To the contrary, the present coating 7 provides a good combination ofthese properties. For example, the present IG unit 110 (and the presentpane 10′, whether monolithic or as part of the IG unit 110) has avisible transmittance T_(v) of greater than 0.5 (i.e., greater than50%). Preferably, the present IG unit 110 (and the present pane 10′,whether monolithic or insulated) achieves a visible transmittance T_(v)of greater than 0.55 (i.e., greater than 55%), or greater than 0.60(i.e., greater than 60%), such as about 0.63.

Further, if the triple silver low-emissivity coating is replaced with adouble silver low-emissivity coating like the LoE²-270™ or LoE²-272™coatings from Cardinal CG Company, then the present IG unit 110 (and thepresent pane 10′, whether monolithic or insulated) can exhibit a visibletransmittance T_(v) of greater than 0.65 (i.e., greater than 65%), oreven greater than 0.67.

Moreover, if the triple silver low-emissivity coating is replaced with asingle silver low-emissivity coating like the LoE-180™ coating fromCardinal CG Company, then the present IG unit 110 (and the present pane10′, whether monolithic or insulated) can exhibit a visibletransmittance T_(v) of greater than 0.70 (i.e., greater than 70%), oreven greater than 0.75.

While the desired level of visible transmittance can be selected andvaried to accommodate different applications, certain preferredembodiments provide a coated pane 10′ having a post-heat-treatmentmonolithic visible transmission of greater than 80%, greater than 82%,or even greater than 85%.

The term “visible transmittance” is well known in the art and is usedherein in accordance with its well-known meaning to refer to thepercentage of all incident visible radiation that is transmitted throughthe IG unit 110. Visible radiation constitutes the wavelength range ofbetween about 380 nm and about 780 nm. Visible transmittance, as well asvisible reflectance, can be determined in accordance with NFRC 300-2014,Standard Test Method for Determining the Solar and Infrared OpticalProperties of Glazing Materials and Fading Resistance of Systems. Thewell-known WINDOW 7.1 computer program can be used in calculating theseand other reported optical properties.

The present coating 7 can provide a visible absorption of less than 10%.Preferably, the visible absorption is less than 5% (e.g., after heattreatment).

The present coating 7 can achieve desirable reflected color propertiesin combination with excellent thermal insulating properties. Forexample, the present IG unit 110 preferably exhibits an exteriorreflected color characterized by an “a” color coordinate of between −7and 2 (e.g., between −5 and 1, such as about −1.9) and a “b” colorcoordinate of between −9 and 0 (e.g., between −6 and −1, such as about−3.4).

The present discussion of color properties is reported using thewell-known color coordinates of “a” and “b.” In more detail, these colorcoordinates result from conventional use of the well-known Hunter LabColor System (Hunter methods/units, Ill. D65, 10 degree observer). Thepresent color properties can be determined as specified in ASTM Method E308, the relevant teachings of which are incorporated herein byreference.

In certain embodiments, the foregoing color properties are provided incombination with the sheet resistance, emissivity, U value, and visibletransmission properties reported above. For example, the following chartdepicts preferred combinations of properties in accordance with certainembodiments (the tabulated properties are after heat treatment).

preferred more preferred Sheet resistance less than 20 Ω/square lessthan 15 Ω/square emissivity less than 0.25 less than 0.18 U value lessthan 0.3 less than 0.24 T_(vis monolithic) greater than 75% greater than85%

In one embodiment, a multiple-pane insulating glazing unit includes aninternal pane surface bearing a low-emissivity coating that has only onefilm comprising silver. The film comprising silver preferably containsat least 50% silver by weight. The low-emissivity coating is exposed toa between-pane space of the IG unit. A desired one of the two externalpane surfaces bears a coating 7 comprising both an indium tin oxide film20 and a tin oxide film 100. The tin oxide film 100 is located over theindium tin oxide film 20. In the present embodiments, the indium tinoxide film 20 has a sheet resistance of less than 20 ohms/square and athickness of between 1,000 Å and 1,600 Å, while the tin oxide film 100has a thickness of between 90 Å and 1,200 Å, and preferably is devoid ofindium oxide. In the present embodiments, the IG unit has a U value ofless than 0.25 together with a visible transmission of greater than 75%.In addition, the IG unit exhibits an exterior reflected colorcharacterized by an “a_(h)” color coordinate of between −6 and 0 and a“b_(h)” color coordinate of between −8 and −1.

In another embodiment, an IG unit includes an internal pane surfacebearing a low-emissivity coating that has only two films comprisingsilver. Preferably, each film comprising silver contains at least 50%silver by weight. The low-emissivity coating is exposed to abetween-pane space of the IG unit. A desired one of the two externalpane surfaces bears a coating 7 comprising both an indium tin oxide film20 and a tin oxide film 100. The tin oxide film 100 is located over theindium tin oxide film 20. In the present embodiments, the indium tinoxide film 20 has a sheet resistance of less than 20 ohms/square and athickness of between 1,000 Å and 1,600 Å, while the tin oxide film 100has a thickness of between 90 Å and 1,200 Å, and preferably is devoid ofindium oxide. In the present embodiments, the IG unit has a U value ofless than 0.25 together with a visible transmission of greater than 65%.In addition, the IG unit exhibits an exterior reflected colorcharacterized by an “a_(h)” color coordinate of between −6 and 0 and a“b_(h)” color coordinate of between −8 and −1.

In still another embodiment, an IG unit includes an internal panesurface bearing a low-emissivity coating that includes three filmscomprising silver. Preferably, each film comprising silver contains atleast 50% silver by weight. The low-emissivity coating is exposed to abetween-pane space of the IG unit. A desired one of the two externalpane surfaces bears a coating 7 comprising both an indium tin oxide film20 and a tin oxide film 100. The tin oxide film 100 is located over theindium tin oxide film 20. In the present embodiments, the indium tinoxide film 20 has a sheet resistance of less than 20 ohms/square and athickness of between 1,000 Å and 1,600 Å, while the tin oxide film 100has a thickness of between 90 Å and 1,200 Å, and preferably is devoid ofindium oxide. In the present embodiments, the IG unit has a U value ofless than 0.25 together with a visible transmission of greater than 60%.In addition, the IG unit exhibits an exterior reflected colorcharacterized by an “a_(h)” color coordinate of between −6 and land a“b_(h)” color coordinate of between −7 and −1.

In the foregoing three embodiments, the IG unit can, for example, be adouble-pane unit with coating 7 on the #4 surface and the low-emissivitycoating on the #2 surface. Coating 7 can consist of the followinglayers: silicon dioxide at about 100 Å/ITO (90% In/10% Sn) at about1,200-1,400 Å/tin oxide at about 150 Å/SiON at about 900 Å. Thelow-emissivity coating in the first of the foregoing three embodimentscan, for example, be a single-silver low-emissivity coating like thecommercially available LoE-180™ coating from Cardinal CG Company of EdenPrairie, Minn., USA. The low-emissivity coating in the second of theforegoing three embodiments can, for example, be a double-silverlow-emissivity coating like the commercially available LoE²-270™ orLoE²-272™ coatings from Cardinal CG Company. The low-emissivity coatingin the third of the foregoing three embodiments can, for example, be atriple-silver low- emissivity coating like the commercially availableLoE³-366™ coating from Cardinal CG Company.

The invention provides one particular group of embodiments wherein thecoating 7 has an intermediate level of electrical conductivity. In thisparticular group of embodiments, the tin oxide overcoat layer 100, whilepreferred, need not always be present. The sheet resistance andemissivity are higher than the preferred and more preferred rangestabulated above. Specifically, the emissivity ranges from 0.25 to 0.55.The monolithic visible transmission (T_(vis monolithic)) preferably isgreater than 75%, more preferably is greater than 80%, and perhapsoptimally is greater than 85% (e.g., after heat treatment). The visibleabsorption preferably is less than 10%, and more preferably is less than5% (e.g., after heat treatment). In the present embodiments, the indiumtin oxide film preferably has a thickness of between 100 Å and 2,000 Å,such as between 100 Å and 1,200 Å. In some of the present embodiments,the thickness of the indium tin oxide film is greater than 100 Å butless than 1,100 Å, less than 750 Å, less than 500 Å, or even less than300 Å. One exemplary non-heat-treated coating that may be useful for thepresent embodiments has a layer of ITO on a glass substrate, where theITO layer has a thickness of about 1,060 Å. In this case, the emissivityis about 0.45. In another example, a heat-treated coating has thefollowing layer stack: glass/ITO at about 170 Å/SnO₂ at about 1,135Å/SiON at about 560 Å. In this case, the post-heat-treatment emissivityis about 0.5. In still another example, a heat-treated coating has thefollowing layer stack: glass/ITO at about 520 Å/SnO₂ at about 785 Å/SiONat about 560 Å. In this case, the post-heat-treatment emissivity isabout 0.31. If desired, a base coat 15 of the nature describedpreviously may be added to any of these film stacks. Additionally oralternatively, a layer comprising titanium oxide may be added.

The invention also provides methods for producing the present coating 7.In preferred embodiments, the films are deposited by sputtering.Sputtering is well known in the present art.

In accordance the present methods, a substrate 10′ having a surface 18is provided. If desired, this surface 18 can be prepared by suitablewashing or chemical preparation. The present coating 7 is deposited onthe surface 18 of the substrate 10′, e.g., as a series of discretelayers, as a thickness of graded film, or as a combination including atleast one discrete layer and at least one thickness of graded film. Thecoating can be deposited using any thin film deposition technique thatis suitable for depositing the desired film materials at the desired lowhaze and roughness levels. Thus, the present invention includes methodembodiments wherein, using any one or more appropriate thin filmdeposition techniques, the films of any embodiment disclosed herein aredeposited sequentially upon a substrate (e.g., a sheet of glass orplastic). One preferred method utilizes DC magnetron sputtering, whichis commonly used in industry. Reference is made to Chapin's U.S. Pat.No. 4,166,018, the teachings of which are incorporated herein byreference. In some cases, the present coatings are sputtered by AC orpulsed DC from a pair of cathodes. HiPIMS and other modern sputteringmethods can be used as well.

Briefly, magnetron sputtering involves transporting a substrate 10′through a series of low pressure zones (or “chambers” or “bays”) inwhich the various film regions that make up the coating are sequentiallyapplied. To deposit oxide film, the target may be formed of an oxideitself, and the sputtering may proceed in an inert or oxidizingatmosphere. To deposit indium tin oxide, for example, a ceramic indiumtin oxide target can be sputtered in an inert or oxidizing atmosphere.Alternatively, the oxide film can be deposited by sputtering one or moremetallic targets (e.g., of metallic indium tin material) in a reactiveatmosphere. Tin oxide can be deposited by sputtering one or more tintargets in a reactive atmosphere containing oxygen gas. Silicon nitridecan be deposited by sputtering one or more silicon targets (which may bedoped with aluminum or the like to improve conductivity) in a reactiveatmosphere containing nitrogen gas. Silicon oxynitride can be depositedby sputtering one or more silicon targets (which may be doped withaluminum or the like) in a reactive atmosphere containing oxygen andnitrogen gas. Titanium dioxide can be deposited by sputtering one ormore titanium targets (which may be doped with tungsten or the like) ina reactive atmosphere containing oxygen gas. The thickness of thedeposited films can be controlled by varying the speed of the substrate,by varying the power on the targets, or by varying the ratio of power topartial pressure of the reactive gas.

Following is a non-limiting method for depositing one embodiment of thepresent coating 7 onto a glass substrate. A pair of rotatable metallicindium-tin targets is sputtered while an uncoated glass substrate isconveyed past the activated targets at a rate of about 115 inches perminute when depositing the ITO film. In this example, the relativeweight amounts of the two metals in the sputterable material of thetarget is: indium 90%, tin 10%. Here, a power of 6 kW is used for thepair of rotary targets. The sputtering atmosphere is 6 mTorr with a gasflow of 992 sccm of argon and 200 sccm of oxygen. The resulting indiumtin oxide film has a thickness of about 520 Å. Directly over this ITOfilm, a tin oxide film is applied. Here, the tin oxide is applied at athickness of about 785 Å by conveying the glass sheet at about 115inches per minute past a pair of rotary tin targets sputtered at 20 kWin a 6 mTorr atmosphere with a gas flow of 629 sccm of oxygen and 992sccm of argon. Directly over the tin oxide film, a silicon oxynitridefilm is applied at a thickness of about 560 Å by conveying the glasssheet at about 20 inches per minute past a pair of rotary silicontargets (83% Si, 17% Al, by weight) sputtered at 20 kW in a 5 mTorratmosphere with a gas flow of 120 sccm of oxygen and 790 sccm ofnitrogen.

The coated substrate is then heat treated. Various heat treatmentprocesses can be used. For example, the coated substrate can be heattreated on a conventional production tempering line. In tempering, glassis placed in a furnace maintained at about 680-705° C. (preferablycontrolled to 690-700° C.). The glass is typically held in the furnacefor 100-120 seconds with constant movement to better ensure temperatureuniformity of the product. This is intended to raise the glasstemperature to about 640° C. The glass is then removed from the furnaceand placed in a stream of air for about 50 seconds such that the glassis cool enough for an operator to handle. Moreover, as alreadyexplained, the substrate can alternatively be heated prior to filmdeposition, during deposition, or both.

While some preferred embodiments of the invention have been described,it should be understood that various changes, adaptations andmodifications may be made therein without departing from the spirit ofthe invention and the scope of the appended claims.

What is claimed is:
 1. A multiple-pane insulating glazing unit having abetween-pane space and two opposed external pane surfaces, a desired oneof the two external pane surfaces bearing a coating comprising both anindium tin oxide film and a tin oxide film, the tin oxide film beinglocated over the indium tin oxide film.
 2. The multiple-pane insulatingglazing unit of claim 1 wherein the tin oxide film is in contact withthe indium tin oxide film.
 3. The multiple-pane insulating glazing unitof claim 1 wherein the tin oxide film has a thickness of between 90angstroms and 1,200 angstroms.
 4. The multiple-pane insulating glazingunit of claim 1 wherein the indium tin oxide film has a thickness ofbetween 100 angstroms and 2,000 angstroms together with a sheetresistance of less than 50 ohms/square.
 5. The multiple-pane insulatingglazing unit of claim 4 wherein said desired one of the two externalpane surfaces is defined by a glass pane coated with said coating, saidcoated glass pane having a monolithic visible transmission of greaterthan 75%.
 6. The multiple-pane insulating glazing unit of claim 5wherein the sheet resistance of the indium tin oxide film is less than15 ohms/square.
 7. The multiple-pane insulating glazing unit of claim 1wherein the coating further includes an oxynitride film, the oxynitridefilm being located over the tin oxide film.
 8. The multiple-paneinsulating glazing unit of claim 7 wherein the coating further includesa film comprising titanium oxide, the film comprising titanium oxidebeing located over the oxynitride film.
 9. The multiple-pane insulatingglazing unit of claim 1 wherein the multiple-pane insulating glazingunit includes an internal pane surface bearing a low-emissivity coatingthat includes at least one film comprising silver, the low-emissivitycoating being exposed to the between-pane space, the multiple-paneinsulating glazing unit having a U value of less than 0.25 together witha visible transmission of greater than 55%.
 10. A coated pane comprisinga glass substrate and a coating on the glass substrate, the coatingcomprising both an indium tin oxide film and a tin oxide film, the tinoxide film being located further from the glass pane than is the indiumtin oxide film, the indium tin oxide film having a thickness of between100 angstroms and 2,000 angstroms, the tin oxide film having a thicknessof between 90 angstroms and 1,200 angstroms, the indium tin oxide filmhaving a sheet resistance of less than 20 ohms/square, and the coatedpane having a visible transmission of greater than 75%.
 11. The coatedpane of claim 10 wherein the tin oxide film is in contact with theindium tin oxide film.
 12. The coated pane of claim 10 wherein all thefilms of the coating are oxides, nitrides, or oxynitrides.
 13. Thecoated pane of claim 10 wherein the visible transmittance is greaterthan 85%.
 14. The coated pane of claim 10 wherein the thickness of thetin oxide film is between 200 angstroms and 400 angstroms.
 15. Thecoated pane of claim 10 wherein the thickness of the indium tin oxidefilm is between 1,000 angstroms and 1,600 angstroms and its sheetresistance is less than 15 ohms/square.
 16. The coated pane of claim 10wherein the coating further includes an oxynitride film, the oxynitridefilm being located over the tin oxide film.
 17. The coated pane of claim16 wherein the oxynitride film is an exposed outermost film of thecoating and has a thickness of between 100 angstroms and 1,300angstroms.
 18. The coated pane of claim 16 wherein the coating furtherincludes a film comprising titanium oxide, the film comprising titaniumoxide being located over the oxynitride film.
 19. The coated pane ofclaim 10 wherein the coating is devoid of a metal layer.
 20. A coatedpane comprising a glass substrate and a coating on the glass substrate,the coating comprising both an indium tin oxide film and a tin oxidefilm, the coating having an emissivity in the range of from 0.25 to0.55, the tin oxide film being located further from the glass pane thanis the indium tin oxide film, the indium tin oxide film having athickness of greater than 100 Å but less than 1,100 Å, the tin oxidefilm having a thickness of between 90 angstroms and 1,200 angstroms, thecoated pane having a visible transmission of greater than 75%.